LAF1, a MYB transcription activator for phytochrome A signaling

Ballesteros, María Luisa; Bolle, Cordelia; Lois, L. María; Moore, James M.; Vielle‐Calzada, Jean‐Philippe; Grossniklaus, Ueli; Chua, Nam‐Hai

doi:10.1101/gad.915001

Cited by 148 publications

(136 citation statements)

References 86 publications

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“…One possible function for phyB NBs may be to regulate downstream-signaling components, such as transcription factors. Recently, LAF1, a putative transcription factor involved in phyA signaling, was demonstrated to colocalize with COP1 in NBs, and COP1 has been shown to recruit a separate transcription factor, HY5, to NBs (39,40). COP1 is an E3 ubiquitin ligase (40).…”

Section: Discussionmentioning

confidence: 99%

Characterization of the requirements for localization of phytochrome B to nuclear bodies

Meng

Schwab

Chory

2003

Proc. Natl. Acad. Sci. U.S.A.

150

201

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Phytochromes are red-and far-red-sensing photoreceptors that detect the quantity, quality, and duration of light throughout the entire life cycle of plants. Phytochromes accumulate in the cytoplasm in the dark. As one of the earliest responses after light illumination, phytochromes localize to the nucleus where they become associated with discrete nuclear bodies (NBs). Here, we describe the steady-state dynamics of Arabidopsis phytochrome B (phyB) localization in response to different light conditions and define four phyB subnuclear localization patterns: diffuse nuclear localization, small and numerous NBs only, both small and large NBs, and large NBs only. We show that phyB nuclear import is not sufficient for phyB NB formation. Rather, phyB accumulation in NBs is mainly determined by the percentage of the total amount of phyB protein that is in the active phyB conformer, with large NBs always correlating with strong phyB responses. A genetic screen to identify determinants required for subnuclear localization of phyB resulted in several phyB mutants, mutants deficient in phytochrome chromophore biosynthesis, and mutations in at least one previously uninvestigated locus. This study lays the groundwork for future investigations to identify the molecular mechanisms of light-regulated partitioning of plant photoreceptors to discrete subnuclear domains.

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Section: Discussionmentioning

confidence: 99%

Characterization of the requirements for localization of phytochrome B to nuclear bodies

Meng

Schwab

Chory

2003

Proc. Natl. Acad. Sci. U.S.A.

150

201

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“…Dominant-negative A. thaliana mutants of the SUMOconjugating enzyme ESD4 yield plants that are smaller and show delayed flowering (Reeves et al 2002;Murtas et al 2003). A mutation in a putative SUMOylation attachment site of long after far red light 1 (LAF1), a transcriptional activator for phytochrome A signaling, alters LAF1 accumulation in the nucleus (Ballesteros et al 2001). A. thaliana SUMO E3 ligase (SIZ1) gene mutants show altered innate immunity (Lee et al 2007) and an increased susceptibility to drought stress .…”

mentioning

confidence: 99%

The Small Ubiquitin-Like Modifier (SUMO) and SUMO-Conjugating System ofChlamydomonas reinhardtii

Wang¹,

Ladunga²,

Miller

et al. 2008

Genetics

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The availability of the complete DNA sequence of the Chlamydomonas reinhardtii genome and advanced computational biology tools has allowed elucidation and study of the small ubiquitin-like modifier (SUMO) system in this unicellular photosynthetic alga and model eukaryotic cell system. SUMO is a member of a ubiquitin-like protein superfamily that is covalently attached to target proteins as a post-translational modification to alter the localization, stability, and/or function of the target protein in response to changes in the cellular environment. Three SUMO homologs (CrSUMO96, CrSUMO97, and CrSUMO148) and three novel SUMO-related proteins (CrSUMO-like89A, CrSUMO-like89B, and CrSUMO-like90) were found by diverse gene predictions, hidden Markov models, and database search tools inferring from Homo sapiens, Saccharomyces cerevisiae, and Arabidopsis thaliana SUMOs. Among them, CrSUMO96, which can be recognized by the A. thaliana anti-SUMO1 antibody, was studied in detail. Free CrSUMO96 was purified by immunoprecipitation and identified by mass spectrometry analysis. A SUMO-conjugating enzyme (SCE) (E2, Ubc9) in C. reinhardtii was shown to be functional in an Escherichia coli-based in vivo chimeric SUMOylation system. Antibodies to CrSUMO96 recognized free and conjugated forms of CrSUMO96 in Western blot analysis of whole-cell extracts and nuclear localized SUMOylated proteins with in situ immunofluorescence. Western blot analysis showed a marked increase in SUMO conjugated proteins when the cells were subjected to environmental stresses, such as heat shock and osmotic stress. Related analyses revealed multiple potential ubiquitin genes along with two Rub1 genes and one Ufm1 gene in the C. reinhardtii genome.

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“…Levels of phyA and actin were assessed using the ECL PLUS chemiluminescent detection system (Amersham, Buckinghamshire, UK). Northern-blot analysis was conducted as described previously (Møller et al, 2001) using CHS, CAB, PET E, PET H, and XTR7 probes identical to those described elsewhere (Ballesteros et al, 2001;Møller et al, 2001). The 730-bp ASN1 probe was obtained from a cDNA library by PCR-mediated amplification using the oligonucleotides 5Ј-GAGGCACAGAGGACCTGACTGG-3Ј and 5Ј-GAGCCCTCAAGACCA-ACGCAAAAGG-3Ј.…”

Section: Molecular Characterization Of Laf3-1mentioning

confidence: 99%

“…Although the majority of intermediates currently known to be essential for normal seedling responsiveness to activated phyA are predicted to localize to the nucleus (Hoecker et al, 1999;Hudson et al, 1999;Fairchild et al, 2000;Soh et al, 2000;Ballesteros et al, 2001;Dieterle et al, 2001;, others are found exclusively in the cytoplasm (Bolle et al, 2000;Hsieh et al, 2000;Guo et al, 2001) or in both compartments (Choi et al, 1999;Desnos et al, 2001;Zeidler et al, 2001). Plastidic events (Møller et al, 2001) and peroxisomal processes (Hu et al, 2002) also contribute to an intact phyA signaling network.…”

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confidence: 99%

LAF3, a Novel Factor Required for Normal Phytochrome A Signaling

et al. 2003

Self Cite

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Phytochrome A (phyA) is the photolabile plant light receptor that mediates broad spectrum very low-fluence responses and high irradiance responses to continuous far-red light (FR c ). An Arabidopsis mutant laf3-1 (long after far-red 3) was recovered from a screen for transposon-tagged mutants that exhibit reduced inhibition of hypocotyl elongation in FR c . The laf phenotype correlated well with a strongly attenuated disappearance of XTR7 transcript in FR c . The effects of laf3-1 on phyA-controlled CAB, CHS, and PET H expression were more subtle, and the mutation had no clear effects on PET E and ASN1 transcript levels in FR c . The use of two alternative transcription initiation sites in the LAF3 gene generates two isoforms that differ only at their N termini. Transcripts encoding both isoforms were induced during germination and were present at slightly higher levels in de-etiolated seedlings than in those grown in darkness. No significant differential regulation of the two isoforms was observed upon exposure to either FR c or continuous red light. Transcripts encoding the shorter isoform (LAF3 ISF2 ) always appear to be more abundant than those encoding the longer isoform (LAF3 ISF1 ). However, both isoforms were capable of full complementation of the laf3-1 hypocotyl phenotype in FR c . When fused to a yellow fluorescent protein, both isoforms localize to the perinuclear region, suggesting that LAF3 encodes a product that might regulate nucleo-cytoplasmic trafficking of an intermediate(s) involved in phyA signal transduction.Phytochromes are soluble chromoproteins that regulate plant growth and development by their ability to interconvert between two stable spectral forms. Red light (R) converts the R-absorbing Pr form (the form synthesized in darkness) to the Pfr (far-red absorbing form) and far-red light (FR) reconverts Pfr to Pr. Two important features distinguish phytochrome A (phyA) from the other four phytochromes in Arabidopsis. First, although the Arabidopsis phytochromes phyB to phyE are activated exclusively by R and inactivated by irradiation with FR, phyA can be activated by FR and low fluences of R and blue light (B). Secondly, although phyA levels decrease rapidly after exposure to light as a result of both down-regulation of PHYA gene transcription (Cantó n and Quail, 1999) and far greater photolability of phyA than other phytochromes (Sharrock and Clack, 2002), phyA is by far the most abundant phytochrome in etiolated seedlings. These features enable phyA to perform a seminal role in triggering the shift between skotomorphogenesis and photomorphogenesis. Together, they ensure that the inhibition of hypocotyl elongation, and the activation of physiological changes needed to ensure photosynthetic competence are already underway when seedlings emerge from the soil surface. Despite its lability in light-grown plants, the influence of phyA throughout the life cycle is evidenced by its involvement in sensing photoperiod to ensure that flowering is initiated at the proper time (Johnson et al., 199...

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LAF1, a MYB transcription activator for phytochrome A signaling

Cited by 148 publications

References 86 publications

Characterization of the requirements for localization of phytochrome B to nuclear bodies

Characterization of the requirements for localization of phytochrome B to nuclear bodies

The Small Ubiquitin-Like Modifier (SUMO) and SUMO-Conjugating System ofChlamydomonas reinhardtii

LAF3, a Novel Factor Required for Normal Phytochrome A Signaling

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